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Tuesday, September 22 2015

Where were the western diamond-backed rattlesnakes, Crotalus atrox? Jake and I began asking ourselves that question on our first night in Val Verde County, TX, and continued wondering throughout our 10 nights in West Texas. We were no closer to an answer on that 10th night than we had been on the first. We knew only that 14 months earlier (August 2014) we had seen more western diamond-backed rattlers than any other snake species. And that over the years I had found this to often be the case. We found diamond-backs from the time of night that the desert had cooled enough to allow snake movement until the wee hours of the morning when, if we looked eastward, we could see the first evidence of a new dawn. We found them crossing the roadway. We found them quietly coiled, as if basking, on the pavement. We even found them stretched fully out as they swallowed prey, often a kangaroo rat. In other words, there was no shortage of Crotalus atrox. It was other rattlers, black-tails, rock, and Mohave that we had been difficult to see.

But now, a year later, our findings were very different. It was mid-June and we were seeing very few of these big, usually feisty, rattlers. In fact during the 10 days we were in the range of the taxon we saw only 4 C. atrox . 3 were prowling and 1 was coiled in ambush position in a small cave in a low rock cut.

I do have to mention though that where we had seen western diamond-backs a year earlier, we were now encountering rock rattlers in fair numbers, many black-tails. and a few Mohaves. Although the reasons for this species shift remain unclear we actually found the tradeoff quite satisfactory. And I'm already wondering what next year's trip will bring?

More photos under the jump

A western diamond-back consumes its kangaroo rat prey.

This western diamond-back, one of 4 seen in 2015, was in a rockcut cave.